First: Welcome.
Second: this is a help forum, so you'll most probably get help here, if you state the nature of your problem.
Third: you will get more help with a descriptive thread title. Your tile is really not descriptive, there is an Applications help forum already in here.
So, what Mac and Mac OS X version do you have?
Where did you get your version of PS and why does it not want to activate? What steps have you take already?